Motion control of a transporter

ABSTRACT

A transporter for transporting a subject over a surface that may be irregular. The transporter includes a support platform for supporting a load, the loaded support platform defining fore-aft and lateral planes and characterized by a load distribution. A plurality of ground contacting elements are coupled to the support platform such that the transporter is statically stable with respect to tipping in the fore-aft plane. At least one of the plurality of ground contacting elements is driven by a motorized drive arrangement. A sensor module generates a signal indicative of the load distribution. Based at least on the load distribution, a controller commands the motorized drive arrangement.

CROSS REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority from U.S. provisional patentapplication serial No. 60/395,299, filed Jul. 12, 2002, entitled“Control of a Transporter Based on Disposition of the Center ofGravity,” which is hereby incorporated by reference, in its entirety.

TECHNICAL FIELD

[0002] The present invention pertains to transporters and methods fortransporting a load which may be an individual, and more particularly tocontrolling motion of a transporter.

BACKGROUND ART

[0003] A wide range of vehicles having a motorized drive arrangement areknown for conveying various subjects, either for purposive locomotion orfor recreational purposes. The means used by an operator to controlmotion of the motorized drive arrangement of varies greatly. Forexample, an operator may manipulate an accelerator pedal to controlforward motion of an automobile, while steering is typicallyaccomplished using a steering wheel. Or the motion of a sporting vehiclemay be controlled by rocking a foot board upon which a user is standingtowards the front or rear, so as to mechanically move a throttle cable,as described in U.S. Pat. No. 4,790,548 (Francken). Based on theoperator's physical attributes for example, or the transporter'sintended functionality, alternative methods for controlling motion of atransporter may be desirable.

SUMMARY OF THE INVENTION

[0004] In a first embodiment of the invention there is provided atransporter that includes a support platform for supporting a load, theloaded support platform defining fore-aft and lateral planes andcharacterized by a load distribution. A plurality of ground contactingelements are coupled to the support platform such that the transporteris statically stable with respect to tipping in the fore-aft plane. Atleast one of the plurality of ground contacting elements is driven by amotorized drive arrangement. A sensor module generates a signalindicative of a position of the load distribution of the loaded supportplatform. Based at least on the load distribution, a controller commandsthe motorized drive arrangement.

[0005] In accordance with related embodiments of the invention, theplurality of ground contacting elements include at least two wheels. Theat least two wheels may include a first wheel rotatable about a firstaxis and a second wheel rotatable about a second axis, the second axisdisposed aft of the first axis. The controller may be configured so thatfore and aft motion of the transporter is controlled by shifting theload distribution and/or a position of the center of gravity of theloaded support platform fore and aft. The controller may also beconfigured so that lateral motion of the transporter is controlled bylaterally shifting the load distribution and/or position of the centerof gravity of the loaded support platform. The transporter may include auser interface, such as a joystick or a dial, wherein the controllercommands the motorized drive based at least on a signal provided by theuser interface. The sensor module may include a force sensor, a loadsensor, and/or an angular rate sensor such as a tilt sensor that may be,for example, a gyroscope or inclinometer. An offset may be used ingenerating the signal. The offset may be adjustable via a user interfaceon the transporter or a remote control device. The controller maycommand the motorized drive arrangement so as to cause an accelerationof the transporter. The transporter may further include an externallyapprehensible indicator for providing an indication based on motion,such as acceleration. The indicator, which may be a light, may beviewable from behind the transporter.

[0006] In accordance with another embodiment of the invention, a methodfor controlling a transporter having a support platform for supporting aload is presented. The loaded support platform defines fore-aft andlateral planes and is characterized by a load distribution. Thetransporter includes a plurality of ground-contacting elements such thatthe transporter is statically stable with respect to tipping in thefore-aft plane, with a motorized drive arrangement driving at least oneof the plurality of ground-contacting elements. The method includesdetermining the load distribution of the loaded support platform, andcommanding the motorized drive arrangement based at least on the loaddistribtuion.

[0007] In accordance with another embodiment of the invention, atransporter includes a support platform for supporting a load, thesupport platform defining a fore-aft plane and a lateral plane. Aplurality of ground contacting elements are coupled to the supportplatform such that the support platform is statically stable withrespect to tipping in the fore-aft and the lateral plane. A pivotelement is pivotally coupled to at least one of the ground contactingelements such that the pivot element is capable of being tilted by auser interface. A sensor module generates a signal indicative of thetilt of the pivot element. A controller commands a motorized drivearrangement based on the tilt of the pivot element. The motorized drivearrangement drives at least one of the plurality of ground contactingelements.

[0008] In related embodiments of the invention, the pivot element may becapable of tilting in at least the fore-aft plane. The plurality ofground contacting elements may include two laterally disposed wheelsrotatable around an axis, the pivot element pivotally coupled to theaxis. The pivot element may be flexibly coupled to the support platform,via, for example, at least one spring. The user interface may be ahandlebar coupled to the pivot element.

[0009] In accordance with another embodiment of the invention, a methodfor controlling a transporter has a support platform for supporting aload, the support platform defining fore-aft and lateral planes. Thetransporter includes a plurality of ground-contacting elements such thatthe transporter is statically stable with respect to tipping. Thetransporter further includes a pivot element pivotally coupled to atleast one of the ground contacting elements such that the pivot elementis capable of tilting, and a motorized drive arrangement for driving atleast one of the plurality of ground-contacting elements. The methodincludes tilting the pivot element and commanding the motorized drivearrangement as a function of the tilt.

BRIEF DESCRIPTION OF THE DRAWINGS

[0010] The foregoing features of the invention will be more readilyunderstood by reference to the following detailed description, takenwith reference to the accompanying drawings, in which:

[0011]FIG. 1 is an illustration of a side view of a transporter, inaccordance with one embodiment of the invention;

[0012]FIG. 2(a) is an illustration of a side view of a transporter, inaccordance with one embodiment of the invention;

[0013]FIG. 2(b) is an illustration of a side view of a transporter, inaccordance with one embodiment of the invention;

[0014]FIG. 3 is an illustration of a side view of a dynamicallybalancing vehicle;

[0015]FIG. 4 is a block diagram of a controller for controlling themotorized drive of a transporter, in accordance with one embodiment ofthe invention; and

[0016]FIG. 5 is an illustration of a transporter, in accordance with oneembodiment of the invention.

DETAILED DESCRIPTION OF SPECIFIC EMBODIMENTS

[0017] In accordance with one embodiment of the invention, FIG. 1 showsa transporter 10 for bearing a load, which may be a living subject, overthe ground or other surface, such as a floor, which may be referredherein as “ground.” Transporter 10 includes a support platform 11 forsupporting the load. A subject, for example, may stand or sit on supportplatform 11. Attached to support platform 11 may be a handlebar 12 thatcan be gripped while operating the transporter 10.

[0018] Coupled to the support platform 11 are a plurality ofground-contacting elements 13, 14, which provide contact between supportplatform 11 and the ground. Ground-contacting elements may include, butare not limited to, arcuate members, tracks, treads, and wheels(hereinafter the term “wheel” will be used in the specification to referto any such ground contacting element without limitation). Wheels 13, 14help to define a series of axes including the vertical axis, Z-Z, whichis in the direction of gravity through a point of contact of the wheelwith the ground; a lateral axis, Y-Y, which is parallel to the axis ofthe wheels, and a fore-aft axis, X-X, which is perpendicular to thewheel axis. Directions parallel to the axes X-X and Y-Y are called thefore-aft and lateral directions respectively.

[0019] Transporter 10 is statically stable with respect to tipping in atleast the fore-aft plane. To achieve static stability in the fore-aftplane, transporter 10 may include at least a first and second wheel 13,14. The first wheel 13 is rotatable about a first axis, and the secondwheel 14 is rotatable about a second axis that is aft of the first axissuch that the center of gravity of the transporter 10 passes between thefirst and second wheel.

[0020] The motion of transporter 10 is controlled by shifting the loadedsupport platform's center of gravity. It is to be understood that “theposition of the center of gravity” as used herein is an example of amoment of a load distribution. Any mechanism for controlling the motionof the device based on the load distribution is within the scope of thepresent invention as described herein and as claimed in any of theappended claims. Shifting the position of the center of gravity may beaccomplished, for example, by a subject shifting his weight on supportplatform 11. To determine the shift in the center of gravity, thetransporter 10 includes a sensor module. The sensor module generates asignal indicative of a position of the center of gravity of the loadedsupport platform with respect to a fiducial point on the transporter 10.

[0021] Sensor module includes at least one sensor. The at least onesensor may be, without limitation, a load sensor, a force sensor, and/oran angular rate sensor, such as a tilt sensor which may be, for example,a gyroscope or an inclinometer.

[0022] Referring to FIG. 1 for example, transporter 10 includes two loadsensors 15, 16. Load sensor 15 is coupled between the support platform11 and the first wheel 13, while load sensor 16 is coupled between thesupport platform 11 and the second wheel 14. Using the sensed loadsabove each wheel 13 and 14, the position of the center of gravity alongthe fore-aft axis of the transporter 10 can be computed with respect toa fiducial point, such as, but not limited to, the front of the platform11. In various embodiments, a single load sensor may be used. Forexample, if the weight of the loaded support platform is known, thecenter of gravity can be determined using only the one load sensor.Changes in the output from the load sensor(s) that result from theshifting of the loaded support platform's center of gravity can also beused to control the motion of the transporter 10.

[0023]FIG. 2(a) shows another transporter 20, in accordance with oneembodiment of the invention. Transporter 20 includes a support platform21 that is allowed to tilt in the fore-aft plane, based for example, onthe platform's 21 center of gravity, while still being statically stablewith respect to tipping in at least the fore-aft plane. For example andwithout limitation, a pair of springs 26 and 25 may be coupled betweenwheels 23 and 24, respectively, and support platform 31. In otherembodiments, the ground contacting elements 23 and 24 may have somecompliance and serve the function of a spring. Based on the tilting ofthe support platform 21 in the fore-aft plane, at least one sensor 27generates a signal indicative, for example, of a position of the loadedsupport platform's center of gravity. Sensor 27 may be, withoutlimitation: a spring and associated sensor (such as a distance sensor);a load sensor; a tilt sensor such as an inclinometer or a gyroscopewhich provides an inclination of the support platform 21; whiskers; anangular rate sensor; and/or non-contact sensors, such as ultra-sonic oroptical. The tilt may be measured, without limitation, relative togravity, the ground, and/or a reference on the transporter, such as aposition proximate the axis of rotation. Attached to the supportplatform 21 may be a handlebar 22 that can be gripped while operatingthe transporter 20.

[0024] In another embodiment of the invention, FIG. 2(b) shows atransporter 200 that includes a first support platform 290 and a secondsupport platform 210. First support platform 290 is coupled to wheels230 and 240 so as to be statically stable with respect to tipping in thefore-aft plane. Second support platform 210 is coupled to the firstsupport platform 290 such that the second support platform 210 can tiltin the fore-aft plane based, for example, on the second platform's 210center of gravity. Second support platform 210 may be tiltably attachedto the first support platform using, without limitation, springs 250 and260 and/or a pivot mechanism 280. Similar to the above-describedembodiment, based on the tilting of the second support platform 210 inthe fore-aft plane, at least one sensor 270 generates a signalindicative of a position of the second support platform's 210 center ofgravity. Sensor 270 may be, without limitation: a spring and associatedsensor (such as a distance sensor); a load sensor; a tilt sensor such asan inclinometer or a gyroscope which provides an inclination of thesupport platform 507; whiskers; an angular rate sensor; and/ornon-contact sensors, such as ultra-sonic or optical. The tilt may bemeasured, without limitation, relative to gravity, the ground, the firstsupport platform 290 and/or another reference on the transporter.Attached to the first support platform 290 may be a handlebar 220 thatcan be gripped while operating the transporter 200.

[0025] In other embodiments of the invention, the transporter isstatically stable with respect to tipping in both the fore-aft andlateral planes. To provide such stability, the tranporter may includethree or more wheels. The center of gravity may then be determined inboth the fore-aft axis and the lateral axis. For example, force or loadsensors may be coupled between the support platform and each wheel, or atilt sensor(s) may be utilized in combination with springs coupledbetween each wheel.

[0026] In still other embodiments, transporter is statically stable withrespect to tilting in the lateral plane only, as in the case of thehuman transporter described in U.S. Pat. Nos. 5,701,965 and 5,971,091,which are herein incorporated by reference. For example, FIG. 3 shows apersonal transporter designated generally by numeral 38. The personaltransporter 38 includes a support platform 32. A handlebar 34 isattached to the support platform 32. A subject 30 stands on the supportplatform 32, so that the transporter 38 of this embodiment may beoperated in a manner analogous to a scooter. Leaning of the subject 30causes the support platform 32 to tilt, which is sensed by, withoutlimitation, a tilt sensor (not shown). A control loop is provided sothat lean of the subject 30 in a forward or backward direction resultsin the application of torque to wheel 33 about axle 35 thereby causingan acceleration of the vehicle. Vehicle 38, however, is staticallyunstable and requires operation of the control loop to maintain dynamicstability.

[0027] In the above-described embodiments, a controller receives thesignal indicative of a position of the center gravity and/or tilt fromthe sensor module. Based at least on the position of the center ofgravity and/or tilt, the controller commands a motorized drivearrangement for driving one at least one of the plurality of wheels. Thecontroller may also respond to commands from other operator interfaces,such as a joystick or dial attached, for example, to a handlebar.

[0028] In accordance with one embodiment of the invention, the blockdiagram of FIG. 4 shows a controller 40 for controlling the motorizeddrive of the transporter. Controller 40 receives an input characteristicof a position of the center of gravity and/or tilt of the loaded supportplatform from sensor module 44. Based at least on the input from thesensor module 44, controller 40 commands at least one motorized drive45, 46. Controller 40 also interfaces with a user interface 41 and awheel rotation sensor 43. User interface 41 may, for example, includecontrols for turning the controller 40 on or off. When the controller 40is turned off, the transporter's wheels may be free to move, such thattransporter acts as a typical push scooter. User interface 41 may alsocontrol a locking mechanism 42 for locking one or more wheels of thetransporter.

[0029] The controller 40 includes a control algorithm to determine theamount of torque to be applied to one or both wheels based on theposition of the center of gravity and/or tilt of the loaded supportplatform. The control algorithm may be configured either in design ofthe system or in real time, on the basis of current operating mode andoperating conditions as well as preferences of the user. Controller 40may implement the control algorithm by using a control loop. Theoperation of control loops is well known in the art of electromechanicalengineering and is outlined, for example, in Fraser & Milne,Electro-Mechanical Engineering, IEEE Press (1994), particularly inChapter 11, “Principles of Continuous Control” which is incorporatedherein by reference.

[0030] As an example, and not meant to be limiting, the controlalgorithm may take the form:

Torque Command=K·(C+O)

[0031] where K=gain,

[0032] C=a vector defining the loaded support platform's center ofgravity with respect to a fiducial point on the transporter, and

[0033] O=offset.

[0034] The loaded support platform's position of center of gravity, C,may be in the form of an error term defined as the loaded platform'sdesired position of center of gravity minus the loaded platform's sensedposition of center of gravity. The loaded platform's desired position ofcenter of gravity may be a predetermined constant in the controlalgorithm. Alternatively, a subject on the transporter may control thesetting of the platform's desired position of center of gravity via userinterface 41. For example, upon stepping onto the platform and prior toallowing movement of the transporter, a subject may activate a switch onthe transporter's handlebar that triggers determination of the desiredposition of center of gravity based on inputs received from the sensormodule 44 This allows the subject to acquire a known initial position,from which the subject can then deviate so as to cause a change in theloaded platform's position of center of gravity.

[0035] The gain, K, may be a predetermined constant, or may beentered/adjusted by the operator through user interface 41. Gain K is,most generally, a vector, with the torque determined as a scalar productof the gain and the center-of-gravity displacement vector.Responsiveness of the transporter to changes in the loaded supportplatform's center of gravity can be governed by K. For example, if themagnitude of at least one element of vector K is increased, a rider willperceive a stiffer response in that a small change in the loadedplatform's position of center of gravity will result in a large torquecommand.

[0036] Offset, O, may be incorporated into the control algorithm togovern the torque applied to the motorized drive, either in addition to,or separate from, the direct effect of C. Thus, for example, the usermay provide an input by means of a user interface 41 of any sort, theinput being treated by the control system equivalently to a change, forexample, in the loaded platform's position of center of gravity.

[0037] Thus, in the above-described embodiments of the invention, motionof the transporter may be controlled by changing the loaded platform'scenter of gravity, such as by the operator leaning or alternatively,changing his position on the platform. Depending on the controlalgorithm, an initial change in the center of gravity in the foredirection may result in positive torque being applied to at least one ofthe wheels, causing the wheels to move forwards. Likewise, an initialchange in the center of gravity in the aft direction may result in anegative torque applied to at least one of the wheels, causing thewheels to move in the aft direction. If the subject then continues tolean (or remains in his changed position on the platform) such that thecenter of gravity of the loaded platform remains the same, the motorwill continue to torque at approximately the same rate.

[0038] As described above, in addition to being statically stable in thefore-aft plane, the transporter may also be statically stable withrespect to tipping in the lateral plane, with a signal representative ofthe position of the center of gravity being determined in either or bothfore-aft and lateral directions. In such embodiments, lateral shifts inthe center of gravity of the loaded platform can be used eitherseparately or in combination with shifts in the center of gravity in thefore-aft plane to control motion of the transporter. For example, andnot meant to be limiting, fore-aft shifts in the center of gravity ofthe loaded support platform can control fore-aft motion, while lateralshifts in the center of gravity control steering of the transporter.

[0039] Steering may be accomplished in an embodiment having at least twolaterally disposed wheels (i.e., a left and right wheel), by providing,for example, separate motors for left and right wheels. Torque desiredfor the left motor and the torque desired from the right motor can becalculated separately. Additionally, tracking both the left wheel motionand the right wheel motion permits adjustments to be made, as known topersons of ordinary skill in the control arts, to prevent unwantedturning of the vehicle and to account for performance variations betweenthe two motors.

[0040] In accordance with another embodiment of the invention, FIG. 5shows a transporter 501 that includes a support platform 502 capable ofsupporting a load. The support platform 501 is coupled to a plurality ofwheels 503 and 504 and is statically stable with respect to tipping inboth the fore-aft and lateral planes. A pivot element 507 is pivotallycoupled to at least one of the wheels 503 and 504, such that the pivotelement 507 is capable of tilting. For example, the plurality of groundcontacting elements may include two laterally disposed wheels, rightwheel 504 and left wheel (not shown), rotatable around an axis 545,wherein the pivot element 507 is pivotally coupled to the axis 545 suchthat pivot element 507 can tilt in the fore-aft plane.

[0041] Tilting of the pivot element 507 is accomplished via an operatorinterface, which may be, without limitation, a handlebar 512. Handlebar512 is coupled to the pivot element 507 such that, for example, a tiltof the handlebar 512 in the fore-aft direction results in acorresponding tilt of pivot element 507.

[0042] At least one sensor 555 generates a signal indicative of the tiltof the pivot element 507. Sensor 555 may be, without limitation: aspring and associated sensor (such as a distance sensor); a load sensor;a tilt sensor such as an inclinometer or a gyroscope which provides aninclination of the support platform 507; whiskers; an angular ratesensor; and/or non-contact sensors, such as ultra-sonic or optical. Thetilt may be measured, without limitation, relative to gravity, theground, and/or a reference on the transporter, such as a positionproximate the axis of rotation. A controller controls a motorized drivearrangement drives at least one wheel 504 based at least on the tilt.

[0043] In various embodiments, the pivot element 507 is flexibly coupledto support platform 502, for example, by a plurality of springs 508-509.This allows the pivot element platform 507 to maintain a predeterminedtilt when the handlebar 512 is not manipulated. In various embodiments,the controller may be preset so as to command a specified motion basedon the predetermined tilt. For example, when the predetermined tilt issensed, controller may command no motion to the motorized drivearrangement. Responsiveness of the transporter can also be controlledvia springs 508-509.

[0044] As in above-described embodiments, steering of the transporter501 may be controlled by any number of user interfaces known in the art,such as, without limitation, a joystick or thumbwheel positioned on orin close proximity to the handlebar. Motorized drive arrangement mayhave separate motors, as described above, for separately drivinglaterally disposed left (not shown) and right wheels 504 based onsignals received from the user interface. Laterally disposed left wheel(not shown) and right wheel 503 may be, for example, caster wheels thatare capable of turning around a vertical axis to support turning oftransporter 501.

[0045] In above-described embodiments of the invention, the transportermay include an indicator, referred to as reference number 540 in FIG. 5.Indicator 540 is apprehensible externally, based on motion commanded viathe motorized drive arrangement. For example, the indicator 540 may bebased on acceleration commanded. The externally apprehensible indication540 may include, without limitation, a light that can be illuminated.

[0046] The described embodiments of the invention are intended to bemerely exemplary and numerous variations and modifications will beapparent to those skilled in the art. All such variations andmodifications are intended to be within the scope of the presentinvention as defined in the appended claims.

What is claimed is:
 1. A transporter comprising: a support platform forsupporting a load, the loaded support platform defining fore-aft andlateral planes and characterized by a load distribution; a plurality ofground contacting elements coupled to the support platform such that thetransporter is statically stable with respect to tipping in the fore-aftplane; a motorized drive arrangement for driving at least one of theplurality of ground contacting elements; a sensor module for generatinga signal indicative of the load distribution of the loaded supportplatform; and a controller for commanding the motorized drivearrangement based on the load distribution.
 2. The transporter accordingto claim 1, wherein the plurality of ground contacting elements includeat least two wheels.
 3. The transporter according to claim 2, whereinthe at least two wheels include: a first wheel rotatable about a firstaxis; and a second wheel rotatable about a second axis, the second axisdisposed aft of the first axis.
 4. The transporter according to claim 1,wherein the controller is configured so that fore and aft motion of thetransporter is controlled by shifting the load distribution of theloaded support platform fore and aft.
 5. The transporter according toclaim 1, wherein the loaded support platform is characterized by acenter of gravity having a position, and wherein the controller isconfigured so that fore and aft motion of the transporter is controlledby shifting the position of the center of gravity of the loaded supportplatform fore and aft.
 6. The transporter according to claim 1, whereinthe controller is configured so that turning of the transporter iscontrolled by laterally shifting the load distribution of the loadedsupport platform.
 7. The transporter according to claim 1, wherein theloaded support platform is characterized by a center of gravity having aposition, wherein the controller is configured so that turning of thetransporter is controlled by laterally shifting the position of thecenter of gravity of the loaded support platform.
 8. The transporteraccording to claim 1, wherein the plurality of ground contactingelements are coupled to the support platform such that the transporteris statically stable with respect to tipping in both the fore-aft andlateral planes.
 9. The transporter according to claim 1, wherein thesensor module includes at least one sensor selected from the group ofsensors consisting of a load sensor, force sensor, and a tilt sensor.10. The transporter according to claim 1, wherein the sensor module addsan offset in generating the signal.
 11. The transporter according toclaim 10, wherein the offset is adjustable via a user interface.
 12. Thetransporter according to claim 1, wherein the controller commands themotorized drive arrangement so as to cause an acceleration of thetransporter, the transporter further including an indicator forproviding an indication based on the acceleration, the indicationapprehensible externally.
 13. The transporter according to claim 1,wherein the indicator is viewable from behind the transporter.
 14. Thetransporter according to claim 1, wherein the transporter furtherincludes a user interface, wherein the controller commands the motorizeddrive arrangement based at least on a signal provided by the userinterface.
 15. A transporter according to claim 14, wherein the userinterface is selected from the group of user interfaces consisting of ajoystick and a dial.
 16. A method for controlling a transporter having asupport platform for supporting a load, the loaded support platformdefining fore-aft and lateral planes and characterized by a loaddistribution, the transporter further including a plurality ofground-contacting elements such that the transporter is staticallystable with respect to tipping in the fore-aft plane, the transporterfurther including a motorized drive arrangement for driving at least oneof the plurality of ground-contacting elements, the method comprising:determining the load distribution of the loaded support; commanding themotorized drive arrangement based at least on the load distribution. 17.The method according to claim 16, wherein determining the loaddistribution of the loaded platform includes sensing a load above atleast one ground-contacting element.
 18. The method according to claim16, wherein determining the load distribution of gravity of the loadedplatform includes sensing a tilt of the loaded support platform.
 19. Themethod according to claim 16, wherein determining the load distributionof the loaded platform includes sensing a roll angle of the loadedsupport platform.
 20. The method according to claim 16, whereincommanding the motorized drive is further based on a control signal froma transporter user interface.
 21. The method according to claim 16,further comprising providing an externally apprehensible indicationbased on motion commanded.
 22. The method according to claim 21, whereinproviding the externally apprehensible indication is based onacceleration commanded.
 23. The method according to claim 22, whereinproviding the externally apprehensible indication includes illuminatinga light.
 24. A transporter comprising: a support platform for supportinga load, the support platform defining a fore-aft plane and a lateralplane; a plurality of ground contacting elements coupled to the supportplatform such that the support platform is statically stable withrespect to tipping in the fore-aft and the lateral plane; a pivotelement pivotally coupled to at least one of the ground contactingelements such that the pivot element is capable of tilting; a userinterface for causing a tilt of the pivot element; a sensor module forgenerating a signal indicative of the tilt of the pivot element; amotorized drive arrangement for driving at least one of the plurality ofground contacting elements; and a controller for commanding themotorized drive arrangement based on the tilt of the pivot element. 25.The transporter according to claim 24, wherein the pivot element iscapable of tilting in at least the fore-aft plane.
 26. The transporteraccording to claim 24, wherein the plurality of ground contactingelements include two laterally disposed wheels rotatable around an axis,the pivot element pivotally coupled to the axis.
 27. The transporteraccording to claim 24, wherein the pivot element is flexibly coupled tothe support platform.
 28. The transporter according to claim 27, whereinthe pivot element is flexibly coupled to the support platform via atleast one spring.
 29. The transporter according to claim 24, wherein theuser interface is a handlebar coupled to the pivot element.
 30. A methodfor controlling a transporter having a support platform for supporting aload, the support platform defining fore-aft and lateral planes, thetransporter including a plurality of ground-contacting elements suchthat the transporter is statically stable with respect to tipping, thetransporter further including a pivot element pivotally coupled to atleast one of the ground contacting elements such that the pivot elementis capable of tilting, and a motorized drive arrangement for driving atleast one of the plurality of ground-contacting elements, the methodcomprising: causing a tilt of the pivot element; and commanding themotorized drive arrangement based at least on the tilt.
 31. A methodaccording to claim 30, wherein causing the tilt includes tilting ahandlebar coupled to the pivot element.
 32. A method according to claim30, further comprising flexibly coupling the pivot element to thesupport platform.